Features: Output voltage options:2.0V ± 5%, 1.8V ± 5%, and 1.5V ± 6%
120mA output current capability
Multi-Gain and Gain Hopping for Highest Possible Efficiency - up to 90% Efficient
2.6V to 5.5V input range
Input and Output Voltage Monitoring (BATOK and POK)
Low operating supply current: 35A
Shutdown supply current: 0.1A
Thermal and short circuit protection
LM2798 turn-on time: 400s LM2797 turn-on time: 100s
Available in an 10-Pin MSOP PackageApplicationCellular Phones
Pagers
H/PC and P/PC Devices
Portable Electronic Equipment
Handheld InstrumentationPinout
SpecificationsIf Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.
VIN, EN, POK, BATOK pins: Voltage
to Ground (Note 3) |
−0.3V to 5.6V |
| Junction Temperature (TJ-MAX-ABS) |
150°C |
Continuous Power Dissipation
(Note 4) |
Internally Limited |
VOUT Short-Circuit to GND Duration
(Note 4) |
Unlimited |
| Storage Temperature Range |
−65°C to 150°C |
Lead Temperature
(Soldering, 5 Sec.) |
260°C |
ESD Rating (Note 5)
Human-body model: |
2 kV |
| Machine model |
200V |
| Output Current |
120 mA |
| Output Min |
2.0, 1.8, 1.5 Volt |
| Output Max |
2.0, 1.8, 1.5 Volt |
| Adjustable Output |
No |
| Input Min Voltage |
2.6 Volt |
| Input Max Voltage |
5.5 Volt |
| Frequency Min |
500 kHz |
| Frequency Max |
500 kHz |
| Efficiency (peak) |
90 % |
| Adj Switch Frequency |
No |
| On/Off Pin |
Yes |
| Quiescent Current |
0.035 mA |
| Special Features |
Output-OK and battery-OK flags |
| PWM Mode |
Multiple Fractional Gain SwCap |
| Topology |
SwCap Buck |
| Step-Down |
Yes |
| Step-Up |
No |
| Inverting |
No |
| RegType |
Switched Cap Regulator |
| PowerWise |
Yes |
| Temperature Min |
-40 deg C |
| Temperature Max |
85 deg C |
| View Using Catalog |
DescriptionThe LM2798 switched capacitor step-down DC/DC converters efficiently produce a 120mA regulated low-voltage rail from a 2.6V to 5.5V input. Fixed output voltage options of 1.5V, 1.8V, and 2.0V are available. The LM2797/98 uses multiple fractional gain configurations to maximize conversion efficiency over the entire input voltage and output current ranges. Also contributing to high overall efficiency is the extremely low supply current of the LM2797/98: 35A operating unloaded and 0.1A in shutdown.
Features of the LM2798 include input voltage and output voltage monitoring. Pin BATOK provides battery monitoring by indicating when the input voltage is above 2.85V (typ.). Pin POK verifies that the output voltage is not more than 5% (typ.) below the nominal output voltage of the part.
The optimal external component requirements of the LM2798 solution minimize size and cost, making the part ideal for Li-Ion and other battery powered designs. Two 1F flying capacitors and two 10F bypass capacitors are all that is required, and no inductors are needed.
The LM2798 also features short-circuit protection overtemperature protection, and soft-start circuitry to prevent excessive inrush currents. The LM2798 has a 400s turn-on time. The turn-on time of the LM2797 is 100s.
LM2798 Data Sheet
